Demi Lovato marked a very important milestone on Monday – her six-year anniversary with her boyfriend Wilmer Valderrama. The singer is head over heels in love with her man, judging by one of her latest Instagram posts.

Demi gave fans a snapshot of her love life, posting a photo of herself and Wilmer, 35, snuggled up in bed. The 23-year-old simply captioned the selfie: "6 ❤".

Demi then followed it up with a carefully crafted collage of the lovebirds through the years.

"You can see from our Instagrams that we're very sweet to one another," said Demi Lovato

The pair met when the singer was 18 and the actor was 30. "People were definitely judgmental and even my parents were kind of, 'Why is someone his age wanting to date someone so young?'" Demi told New Zealand radio show last year.

"And after a while everyone around us started to see what we have is real and incredible and very special, and we've been together ever since.

"Obviously my family loves him [now]. People kind of stop doing that because you can see when we're together or even just from our Instagrams that we're very sweet to one another."

The singer first started dating Wilmer when she was 18

Demi also admitted that one day she would like to marry Wilmer. "I am very, very in love with him," she said. "I think we'll probably wait a bit longer, but if he asked tomorrow, I'd say yes."

Last year the formerjudge was forced to set the record straight, clarifying that she and Wilmer were not engaged. After posting a photo of the couple holding hands, fans noticed that Demi was wearing a gold band on her ring finger.

"He's there for me when other's aren't… He supports me when others won't… He loves me when others don't," Demi wrote, before editing to add: "(not engaged… y'all are crazy)."

On the prospect of marriage, Demi said: "If he asked tomorrow, I'd say yes"

The former star of has been with Demi through thick and thin. Wilmer has stayed by Demi's side through her rough patches and stints at rehab for alcohol, drug abuse and her eating disorder.

The few times that they did temporarily split was at the beginning of their relationship when Demi admitted she "just wanted to sabotage" everything around her. The singer is now back to her happy and healthy self, and no doubt has Wilmer to thank for.

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